The Future of Biological Selectors

While most operators today would not consider attempting on and off cycle times for blower operation due to its complexity, this will likely change with the advent of biological selector system implementation. The environmental state of a process can be identified by measuring the oxidation reduction potential (ORP). Stress on microbes can be applied by varying this environmental state. Turning...

Facultative bacteria exist at an ORP state well above the level where hydrogen sulfide gas is released and — even further — above where methane gas is released. This results in being able to operate a wastewater treatment process without the odors associated with these two gases.

The waste sludge bio-selector process illustrates that side stream processes can be used to develop strong colonies of facultative bacteria. This side stream bio-selector process can enhance nutrient removal processes that are being utilized in the main flow stream of a water resource recovery facility. Current nutrient removal processes utilize high volume (internal) flow recycling. In the...

Performing this process requires a diffused aeration and mixing system that can operate in these high solids processes and not fail due to system clogging and air blockage.

Design engineers at Red Valve Co. (Pittsburgh) are currently developing a control equation for the operation of a bio-selector. The key is first to understand the relationship of the control parameters and their effect on the process fluid’s ability to generate the required stress periods for biological selection. These stress periods have very specific ORP ranges and exposure time limits.

The future of biological selectors, especially side stream treatment processes, has significant potential in reducing the current costs associated with nutrient removal processes. These current methods are requiring excessive energy for blower operation, supplemental mixing energy and pump recirculation energy as well as the capital cost associated with these configurations.